A filter insert of the above specified kind is known for example from EP1016449B1. In this filter insert the individual filter bags are sealed one against the other by means of cast resin. Connections of the filter bags are formed after hardening of the cast resin. As a result, the sealing of the filter bags one to the other is rather complex.
Further, it is known in the art to insert a heating wire between abutting edges of the frames of adjacent filter bags. The heating wire is energized and the frames of adjacent filter bags are welded together. The heating wire then remains in the filter insert. This configuration leads also to a huge effort for sealing the filter bags one against the other.
The leak tightness of the connection of the filter bags one against the other at the filtrate collecting space is, however, crucial for this kind of filter insert, because at this very position the dirty section is separated from the clean section which comprises the filtrate collecting space. Since the filter insert mostly comprises a multitude of filter bags the filtrate collecting space has a multitude of sealing points.